Largest recent impact craters on Mars: Orbital imaging and surface seismic co-investigation.

Two >130-meter-diameter impact craters formed on Mars during the later half of 2021. These are the two largest fresh impact craters discovered by the Mars Reconnaissance Orbiter since operations started 16 years ago. The impacts created two of the largest seismic events (magnitudes greater than 4) recorded by InSight during its 3-year mission. The combination of orbital imagery and seismic ground motion enables the investigation of subsurface and atmospheric energy partitioning of the impact process on a planet with a thin atmosphere and the first direct test of martian deep-interior seismic models with known event distances. The impact at 35°N excavated blocks of water ice, which is the lowest latitude at which ice has been directly observed on Mars.

Seasonal erosion and restoration of Mars' northern polar dunes.

Despite radically different environmental conditions, terrestrial and martian dunes bear a strong resemblance, indicating that the basic processes of saltation and grainfall (sand avalanching down the dune slipface) operate on both worlds. Here, we show that martian dunes are subject to an additional modification process not found on Earth: springtime sublimation of Mars' CO(2) seasonal polar caps. Numerous dunes in Mars' north polar region have experienced morphological changes within a Mars year, detected in images acquired by the High-Resolution Imaging Science Experiment on the Mars Reconnaissance Orbiter. Dunes show new alcoves, gullies, and dune apron extension. This is followed by remobilization of the fresh deposits by the wind, forming ripples and erasing gullies. The widespread nature of these rapid changes, and the pristine appearance of most dunes in the area, implicates active sand transport in the vast polar erg in Mars' current climate.

A closer look at water-related geologic activity on Mars.

Water has supposedly marked the surface of Mars and produced characteristic landforms. To understand the history of water on Mars, we take a close look at key locations with the High-Resolution Imaging Science Experiment on board the Mars Reconnaissance Orbiter, reaching fine spatial scales of 25 to 32 centimeters per pixel. Boulders ranging up to approximately 2 meters in diameter are ubiquitous in the middle to high latitudes, which include deposits previously interpreted as finegrained ocean sediments or dusty snow. Bright gully deposits identify six locations with very recent activity, but these lie on steep (20 degrees to 35 degrees) slopes where dry mass wasting could occur. Thus, we cannot confirm the reality of ancient oceans or water in active gullies but do see evidence of fluvial modification of geologically recent mid-latitude gullies and equatorial impact craters.

Athabasca Valles, Mars: a lava-draped channel system.

Athabasca Valles is a young outflow channel system on Mars that may have been carved by catastrophic water floods. However, images acquired by the High-Resolution Imaging Science Experiment camera onboard the Mars Reconnaissance Orbiter spacecraft reveal that Athabasca Valles is now entirely draped by a thin layer of solidified lava-the remnant of a once-swollen river of molten rock. The lava erupted from a fissure, inundated the channels, and drained downstream in geologically recent times. Purported ice features in Athabasca Valles and its distal basin, Cerberus Palus, are actually composed of this lava. Similar volcanic processes may have operated in other ostensibly fluvial channels, which could explain in part why the landers sent to investigate sites of ancient flooding on Mars have predominantly found lava at the surface instead.

Herbaceous vegetation productivity, persistence, and metals uptake on a biosolids-amended mine soil.

The selection of plant species is critical for the successful establishment and long-term maintenance of vegetation on reclaimed surface mined soils. A study was conducted to assess the capability of 16 forage grass and legume species in monocultures and mixes to establish and thrive on a reclaimed Appalachian surface mine amended with biosolids. The 0.15-ha coarse-textured, rocky, non-acid forming mined site was prepared for planting by grading to a 2% slope and amending sandstone overburden materials with a mixture of composted and dewatered, anaerobically digested biosolids at a rate of 368 Mg ha(-1) (dry weight). Tall fescue (Festuca arundinacea Schreb.), orchardgrass (Dactylis glomerata L.), switchgrass (Panicum virgatum L.), caucasian bluestem (Bothriochloa caucasia L.), reed canarygrass (Phalaris arundinacea L.), ladino clover (Trifolium repens L.), birdsfoot trefoil (Lotus corniculatus L.), crownvetch (Coronilla varia L.), alfalfa (Medicago sativa L.), common sericea lespedeza and AULotan sericea lespedeza (Lespedeza cuneata L.), tall fescue-ladino clover, tall fescue-alfalfa, orchardgrass-birdsfoot trefoil, switchgrass-AULotan, and an herbaceous species mix intended for planting on reforested sites consisting of foxtail millet [Setaria italica (L.) Beauv.], perennial ryegrass (Lolium perenne L.), redtop (Agrostis alba L.), kobe lespedeza (Kummerowia striata L.), appalow lespedeza (Lespedeza cuneata L.), and birdsfoot trefoil were established between spring 1990 and 1991. Vegetative biomass and/or persistence were assessed in 1996, 1997, 1998, 2000, 2001, and 2002. The high rate of biosolids applied provided favorable soil chemical properties but could not overcome physical property limitations due to shallow undeveloped soil perched atop a compacted soil layer at 25 cm depth. The plant species whose persistence and biomass production were the greatest after a decade or more of establishment (i.e., switchgrass, sericea lespedeza, reed canarygrass, tall fescue, and crownvetch) shared the physiological and reproductive characteristics of low fertility requirements, drought and moisture tolerance, and propagation by rhizome and/or stolons. Of these five species, two (tall fescue and sericea lespedeza) are or have been seeded commonly on Appalachian coal surface mines, and often dominate abandoned pasture sites. Despite the high rates of heavy metal-bearing biosolids applied to the soil, plant uptake of Cd, Cu, Ni, and Zn were well within critical concentrations more than a decade after establishment of the vegetation.

Induction agents for day-case anaesthesia. A double-blind comparison of propofol and midazolam antagonised by flumazenil.

Early postoperative recovery was studied using sedation scoring, measurement of flicker fusion frequency and completion of Trieger test figures in 60 male patients who presented for vasectomy under general anaesthesia as day patients. Anaesthesia was induced in groups 1 and 2 (20 patients each) with mean (SD) doses of 0.16 (0.04) mg/kg or 0.16 (0.03) mg/kg midazolam respectively; group 2 received flumazenil 0.55 (0.19) mg after completion of surgery. The remaining 20 patients (group 3) received propofol 1.50 (0.24) mg/kg. Anaesthesia was maintained with isoflurane vaporized in 33% oxygen and nitrous oxide in all patients. Flumazenil tended to improve tests of recovery after midazolam anaesthesia, but early recovery after propofol anaesthesia was associated with better psychomotor test results and less impairment of mental state as judged by sedation and amnesia scoring.

The value of flumazenil in the reversal of midazolam-induced sedation for upper gastrointestinal endoscopy.

Fifty patients who underwent diagnostic upper gastrointestinal endoscopy after midazolam sedation were randomized to receive (after completion of the examination) either the benzodiazepine receptor antagonist flumazenil or an identical-looking placebo. The speed of recovery from sedation was assessed by reaction time testing, measurement of critical flicker fusion frequency, and the semi-quantitative SOCA scoring system. Measurements were made up to 6 h post examination in all subjects, and at 12 and 24 h in all in-patients (n = 20). Flumazenil-treated patients were significantly more alert than those who received placebo at 10 min, 30 min, 1 h and 2 h (P less than 0.001 in all instances). Thereafter the two groups were similar. There was no evidence of recurrence of sedation in flumazenil-treated patients, nor did this drug adversely affect the period of anterograde amnesia between the administration of midazolam and flumazenil.

Anaesthetic agents and their effect on tissue protein synthesis in the rat.

1. Rates of protein synthesis were measured, in vivo, in lung, liver, heart and skeletal muscle of young male rats. Groups of rats were exposed for 1 h duration to one of the following anaesthetic regimens: 1.4% halothane, 2.2% halothane, 1.4% halothane in 66% nitrous oxide, intravenous pentobarbitone (20 mg/kg) and intravenous midazolam (18 mg/kg) combined with fentanyl (2 micrograms/kg). Fractional rates of protein synthesis were determined by injecting [3H]phenylalanine (150 mumol/100 g body weight). 2. Liver protein synthesis was depressed significantly by all regimens, except midazolam/fentanyl, by up to 37.7% of control values. Lung protein synthesis was significantly reduced by all the anaesthetic agents by up to 30% of control rates. 3. The effects of the anaesthetic agents on skeletal muscle and heart were small and not statistically significant. 4. There was no evidence of ventilatory depression as manifested by changes in arterial blood gas partial pressures of CO2 and O2, except in the group treated with 2.2% halothane.

Monitoring neuromuscular blockade. The table knife transducer.

A simple and inexpensive force transducer made from a stainless steel table knife is described. Construction is straightforward and utilises strain gauges that are readily available. Amongst its attributes are lightness, ease of application, low sensitivity to postural changes and linearity over extended periods of time.

Effects of H-2 antagonists on the elimination of bupivacaine.

The effects of two histamine H-2 antagonists, cimetidine and ranitidine, on the elimination of bupivacaine were studied in four male volunteers. The cimetidine-treated group demonstrated a statistically significant decrease in clearance of bupivacaine. These results indicate that concomitant administration of cimetidine and bupivacaine may increase the likelihood of toxicity of the latter agent.

A paediatric ventilator with a fluidic control system.

A paediatric ventilator has been designed basically as a fluidic-logic controlled T-piece occluder. Inspiratory and expiratory time, inflation pressure limit, positive end-expiratory pressure (PEEP), continuous positive airway pressure (CPAP) and inspiratory flow-rate are controlled independently and intermittent mandatory ventilation (IMV) is available. Warning systems are provided for failure of the driving as, low airway pressure and inspiratory pressure limit. The breathing circuit is isolated from the control and warning systems for ease of sterilization.